Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
  • F23L15/00—Heating of air supplied for combustion
  • F23L15/04—Arrangements of recuperators
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
  • C03B5/16—Special features of the melting process; Auxiliary means specially adapted for glass-melting furnaces
  • C03B5/235—Heating the glass
  • C03B5/2353—Heating the glass by combustion with pure oxygen or oxygen-enriched air, e.g. using oxy-fuel burners or oxygen lances
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
  • F28D7/00—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall
  • F28D7/16—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits being arranged in parallel spaced relation
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F19/00—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F21/00—Constructions of heat-exchange apparatus characterised by the selection of particular materials
  • F28F21/08—Constructions of heat-exchange apparatus characterised by the selection of particular materials of metal
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E20/00—Combustion technologies with mitigation potential
  • Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P40/00—Technologies relating to the processing of minerals
  • Y02P40/50—Glass production, e.g. reusing waste heat during processing or shaping

Definitions

• the present invention relates to heat exchangers for heating oxygen or a gas rich in oxygen, which are intended for supplying glass melting furnace burners.
• the choice of this type of energy is controlled by economic reasons given the importance of energy consumption.
• As an indication of the usual melting furnaces producing between 600 and 900 tons per day of glass require an available power of the order of 50 to 80 megawatts.
• regenerators are towers lined with refractory in which the combustion gases are first passed to heat the refractories, and in which, in a second time, the air used in the combustion is passed to be heated.
• the alternation of these times leads to a very specific furnace structure.
• the burners are thus on both sides of the melting basin as well as the regenerators associated with them and are generally situated on the opposite side to the active burners. It is not possible to use regenerators to heat the oxygen.
• the generators are always the seat of particle deposits carried by the combustion gases, even if they are previously dusted. The contact of hot oxygen with these deposits is not without risks. It is also difficult to guarantee perfect sealing of these regenerators.
• the air passage and possible leaks are safe but it is not the same for oxygen.
• the object of the invention is therefore to propose solutions that make the use of oxygen, or hot oxygen-rich gases, attractive in the burners of glass melting furnaces, and in particular in furnaces of large capacity.
• the invention also proposes to provide solutions which make this use sufficiently safe, despite the particular technical requirements which are attached to the implementation of oxygen at high temperature.
• the above considerations relating to the use of hot oxygen also apply to gaseous mixtures, in particular with air, in which the oxygen content is sufficiently high.
• their oxygen content is not less than 50%.
• the invention is applicable to gas mixtures whose oxygen content is at least 80%.
• the heating of oxygen, or oxygen-rich gas, for feeding the furnace burners is conducted in exchangers whose exchange capacity is voluntarily limited, without thereby minimizing the temperature at which the oxygen or the oxygen-rich gas is carried.
• the temperature of the oxygen or oxygen-rich gas at the outlet of the exchanger is not less than 300 ° C. and preferably not less than 400 ° C., and the power exchanged in the exchanger for carrying oxygen at these temperatures according to the invention is between 20 and 30OkW, preferably between 40 and 25OkW and particularly preferably between 80 and 170kW.
• the burners used develop significant powers of the order of 1 to 6 MW leading to an oxygen consumption of the order of 200 to 1200 Nm. 3 oxygen per hour.
• each exchanger feeds hot oxygen, or oxygen-rich gas, advantageously and simultaneously, at most three separate burners, each burner may comprise several injection nozzles in the manner as they are presented for example in EP 1 194 719.
• the use of the exchangers according to the invention should preferably lead to limited dimensions, which implies a well-defined mode of operation and in particular, the fact that their conduct makes it possible to develop the power required while keeping the exchange surface as small as possible.
• the exchangers for heating the oxygen, or the oxygen-rich gas advantageously have a power per oxygen contact surface unit with the exchange walls of between 5 and 15 kW / m 2 , and preferably between 7 and 12kW / m 2 .
• the surface considered is that of the wall which separates the oxygen or the oxygen-rich gas from the heat-transfer gas.
• the exchangers used according to the invention must have a structure as simple as possible to avoid the risk of erosion and leakage, because of the aggressiveness of hot oxygen vis-à-vis materials used.
• the exchangers according to the invention are preferably of the tubular type, the oxygen, or the oxygen-rich gas circulating in a bundle of tubes outside which the heat-transfer gas circulates.
• a first way to promote this exchange is to increase the speed of circulation of gases and in particular oxygen, or oxygen-rich gas.
• oxygen or oxygen-rich gas.
• increasing speed is a risk factor.
• the risk is all the more significant as the hot oxygen is likely to cause particles that can react with oxygen and / or whose impact on the walls promotes rapid erosion that is added to that resulting from the friction of oxygen itself.
• the dimensions of the elements of the exchanger are advantageously fixed so that to obtain the necessary power, the speed of oxygen or oxygen-rich gas is not greater than 120m / s at any point of the exchanger, and preferably not more than 100m / s.
• the exchangers according to the invention are also dimensioned such that, for the powers sought, the pressure of the oxygen or oxygen-rich gas in the exchanger does not exceed 3 bars and preferably not
• the energy supply for heating the oxygen or the oxygen-rich gas comes from the combustion gases, either directly by circulation in the exchanger, or preferably indirectly via a fluid which has itself been preheated by an exchange with the combustion gases.
• the intermediate gas in the event of this double exchange is advantageously inert vis-à-vis the oxygen. It is preferably air, nitrogen, CO 2 , water vapor or a mixture of these gases.
• the intermediate gas may consist of a mixture of the inert gases indicated above and a part of the previously dust-free combustion gases.
• the temperature of the fumes can be up to 1550 ° C. and is most often between 1250 and 1450 ° C., and are higher than the temperatures at which the oxygen can be carried without degrading too intensely the material of the walls with which it to be in contact.
• the coolant consisting of air the temperature of the latter after heating by the combustion gases, is preferably between 450 and 1000 0 C, and particularly preferably between 600 and 800 0 C.
• the temperature of the hot oxygen, or gases rich in oxygen, as it results from heat exchange remains within limits for which the choice of materials made according to the invention makes it possible to avoid excessive corrosion of installation.
• This temperature does not ordinarily exceed 900 ° C., and preferably is at most 700 ° C.
• the materials constituting the exchanger, and in the first place those in contact with the hot oxygen must be selected so as to ensure good resistance to oxidation by gases and in particular oxygen in these temperature conditions.
• the resistance sought has several aspects. It's not just about preventing violent oxidation of materials in the form of combustion thereof, it is also a question of preventing an alteration of the surface in contact with oxygen, an alteration which, not only in the long term, may lead to the perforation of the walls, but moreover it is appropriate in certain cases to prevent the pulling of particles which are likely to disturb the subsequent reaction and / or to pollute the products prepared by means of the combustion maintained with this hot oxygen.
• the exchanger to receive gases comprising at least 50% oxygen at a temperature which is not lower than 300 ° C. is constituted, at least for the walls directly in contact with these gas, a metal alloy that satisfies the following test protocol.
• a sample of the metal alloy according to the invention placed in an atmosphere corresponding to the oxygen-rich gas that must circulate in the installation and at the highest temperature encountered in the installation, does not present a weight gain of more than 0.1 mg / cm 2 of exposed surface after 1000 cycles each comprising maintaining at the maximum temperature provided for 1 hour, each plateau at this temperature being followed by a return to ambient temperature.
• the feeding of the burners of the glass furnaces being preferably carried out with a gas whose oxygen content is preferably greater than 80% and can reach 100%, the test indicated above must advantageously be satisfied for these contents.
• the metal alloy chosen supports the same test but whose target temperature is at least 500 ° C., and to satisfy the extreme conditions envisaged, the alloy satisfies the test in which this highest test temperature is at least 600 0 C, and can pass this test even for temperatures of 800 0 C.
• the most suitable alloys for producing the exchanger according to the invention in a self-combustion test in an oxidizing atmosphere, a test corresponding to the ASTM G-124 standard, resist this combustion at least until pressures of 3 bar, and preferably at least up to pressures of 10 bar.
• alloys advantageously used and responding positively to the corrosion test when they are used in temperature ranges greater than 550 ° C., include ferritic-type stainless alloys whose Cr content is between 12 and 30% by weight. weight, and which at the same time include AI at the rate of 1 to
• ferritic type alloys For ferritic type alloys, they become brittle when in temperature ranges of between 400 and 500 ° C. ("embrittlement"). For these reasons, the use of these alloys must take into account the parts considered and the conditions, in particular temperature, prevailing in the exchanger. Parts of the exchanger exposed to hot oxygen can also be made in alloys rich in Ni and Cr, and comprising Ni contents greater than 25% by weight and simultaneously comprising from 10 to 30% of Cr. The Ni content can be up to 75% or more.
• alloys differ from each other in particular in their mechanical properties. Moreover, in their choice, it may be necessary to take into account limitations specific to the intended use. If alloys with a high Ni content are easy to work with, in flat glass production plants, the risk posed by the presence of Ni, the possible entrainment of particles, must be carefully avoided because of the risks of formation in the glass sheets of nickel sulphide generator breaks.
• alloys are resistant to high temperature corrosion by forming a protective film of chromium oxide or alumina.
• the chromium content of the alloy must be high enough to prevent the formation of nickel oxide nodules, which have a rapid increase, and the possible entrainment would be likely to create nickel sulphide in the leaves of glass, generator breaks.
• Ni-rich alloys meeting the stated requirements are those commonly referred to as Inconel 600H, 600L, Incoloy 800H
• alloys whose chromium content is greater than 16% and particularly preferably 20 to 30%.
• Ni-rich alloys meeting the stated requirements are those commonly referred to as Inconel 600H, 600L, 601, 617, 625, Incoloy 800H and 800HT. It is still possible to use an alloy such as 316L stainless steel and 310, easy to work, but the longevity is then less well guaranteed.
• the rate of circulation of the highly oxidizing gases at high temperature is a risk factor for erosion, this can be increased by particles carried by these gases. Initially the gases are well free of solid particles, but these can come from the installation itself. The walls of the pipes and heat exchangers subjected to the corrosion of these gases can indeed release particles whose impact on the downstream elements is also generating erosion and the stronger the higher the velocity of the gases. .
• the surface condition of the walls of the exchanger is likely to influence the corrosion resistance.
• the surfaces of the walls of the exchanger according to the invention in contact with oxygen-rich gases are polished and do not have a roughness of more than 6 micrometers ( ⁇ ).
• ⁇ micrometers
• the roughness is less than 4 ⁇ and most advantageously is at most equal to 2 ⁇ .
• FIG. 1 is a schematic sectional illustration of a gaseous exchanger used according to the invention for heating oxygen or a gas rich in oxygen;
• FIG. 2 is an enlarged partial view of the end of the exchanger shown in FIG. 1;
• FIG. 3 shows a detail of the partial section A of Figure 2.
• the general structure of the exchanger is of the traditional type for gas exchangers. It has an enclosure 1 wrapping a bundle of tubes 2. The tubes are fixed inside the enclosure by plates 3, 4.
• the plates form a sealed wall defining the zone of the enclosure in which circulates the heat transfer gas.
• the circulation of the heat-carrying gas and the oxygen or the gas rich in oxygen advantageously takes place countercurrently.
• the hot heat transfer gas enters the enclosure via the conduit 11, and leaves via the conduit 12 after having traveled through the circuit formed by baffles 13, 14, 15 inside the enclosure.
• the oxygen or oxygen-rich gas circulates in the tubes 2 along a substantially straight path. It enters cold end 16, and hot spring at the end 17 to be led to the burners.
• these tubes end with a flared part.
• This arrangement facilitates the flow of oxygen and its expansion and consequently a certain slowdown.
• this flare is of frustoconical shape with an opening angle ⁇ .
• the caps, and especially the 6 disposed at the oxygen outlet are located at a distance from the ends of the tubes 2. In this way the speed of the oxygen along the walls of the cap is significantly reduced compared with to that which it presents at the exit of the tubes.
• this cap 6 is also chosen so that the progression of the hot oxygen meets the wall of the cap following a low incidence minimizing the impact.
• the wall of the cap is, for example, at an angle of approximately 20 to 30 degrees with respect to the direction of the tubes 2.
• the section of the cap is gradually reduced to the connection with the outlet pipe.
• the sizing of the tubes and their distribution are such that the speed and pressure conditions indicated above are fulfilled for the flow rates used.
• the heat exchanger to be operated continuously for very long periods, despite the precautions to avoid wear of the elements that constitute it, it may happen that a tube no longer has the necessary seal.
• the exchanger is assembled in such a way that the faulty tube can be obstructed at both ends. The operation requires the removal of hats. After the defective tube is taken out of service, the heat exchanger is again usable with a little modified efficiency in proportion to the number of active tubes remaining.
• the samples consist of metal alloy plates 2mm thick and 20x20mm.
• the surface condition of the samples shows a certain importance as regards the sensitivity to oxidation. For this reason one face of each of these plates is polished with an abrasive sheet of SiC up to 1200 grain. The other face is left in its original state, that resulting from industrial rolling.
• the preceding measurements simultaneously comprise the oxidation of the two faces of the sample. Since only one side is polished, the measurement of the oxidation obtained is consequently greater than that which would be observed in practice, when the surface in contact with oxygen is polished.
• the analysis of the modification of the compositions on the surface, and in particular the reduction of the Cr content, is a means of assessing the risk of formation of detachable particles.
• the presence of Cr at a content of not less than 7% guarantees the formation of a protective layer preventing the formation of scales.
• the thickness of the walls may be relatively less thick than was suggested by the prior art. Longevity simulations based on these results lead to walls for the tubes of the exchangers according to the invention, whose thickness may not be greater than 3mm. This thickness can even be equal to or less than 2.5mm.
• the relatively small thickness of the walls of the tubes of the exchanger promotes heat transfer and therefore increases the power available for the same exchange surface.
• an exchanger according to the invention is constituted as follows. It consists of a bundle of 40 Inconel 600 tubes. The outer diameter of the tubes is 17.2mm and the wall thickness is 2.3mm. The tubes have a length of 4000mm.
• the exchange surface in contact with oxygen is then 8.4 m 2 .
• the heat-transfer gas (dust-free air) enters the exchanger at a temperature of 650 ° C.
• the heat-transfer gas flow rate is set at 750 Nm 3 / h.
• the oxygen flow rate is 400 Nm 3 / h. Entering at room temperature the oxygen is heated to 550 ° C.
• the speed of the oxygen in the pipes is 67 m / s, and the pressure drop in the exchanger is less than 0.15 bar.
• a safety system comprising a pressure switch, maintains the pressure in the exchanger at less than lbar.
• the nominal power of the exchanger is 84kW, that per unit area is 9.7kW / m 2 .
• the exchanger supplies oxygen to a glass melting furnace burner with a power of 2MW.
• the complete furnace is supplied with oxygen by exchangers similarly sized.
• the power of each of these exchangers is adapted to best distribute the total power required for driving the oven.

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• 2007
  • 2007-05-10 EP EP07107942A patent/EP1995543A1/fr not_active Withdrawn
• 2008
  • 2008-05-07 WO PCT/EP2008/055615 patent/WO2008141939A2/fr active Application Filing
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  • 2008-05-07 US US12/599,580 patent/US20100258263A1/en not_active Abandoned
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